Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
Greetings!
This is Tin, I'll be happy to assist you. Looks like you're getting Payment Authentication issue to download the MS Office. Have you tried to do the authentication to other browser and check if the issue persists? Just a friendly reminder, no one has access to your account in public forum for your security and privacy.
If the issue persists even trying it on different browser or device, it would be best to reach the MS Accounts & Billing Support:
Kindly open this link: https://support.microsoft.com/contactus/
Ensure that your MS Account has been signed in (the one with the subscription)
Type "Chat with an agent" and hit Enter.
Please click the "Contact support"
Please select the "Products and services"
Please follow the prompts to connect with a live agent.
You may also choose the "Call me back" option if you prefer to receive a call.
Once you're connected to the Live Agent, please let them know about your issue so they could check your account and address your concern.
Thank you,
Tin